The
various Titanium Grades as defined by
ASTM and ASME are numbered from 1 and
upwards where all numbers except 6 and
8 are represented.

Most of
the grades are of alloyed type with various
additions of for example aluminium, vanadium,
nickel, ruthenium, molybdenum, chromium
or zirconium for the purpose of improving
and/or combining various mechanical characteristics,
heat resistance, conductivity, microstructure,
creep, ductility, corrosion resistance
etc. etc.

Palladium
(Pd) and ruthenium (Ru), Nickel (Ni) and
molybdenum (Mo) are elements which can
be added to the pure titanium types in
order to obtain a significant improvement
of corrosion resistance particulary in
slightly reducing environments where titanium
otherwise might face some problems due
to insufficient conditions for formation
of the necessary protective oxidefilm
on the metalsurface. The formation of
a stable and substantially inert protective
oxidefilm on the surface is otherwise
the secret behind the extraordinary corrosion
resistance of titanium . The mechnical
properties of commercially pure titanium
are in fact controlled by "alloying"
to various levels of oxygen and nitrogen
to obtain strength levels varying between
approximately 290 and 550 MPa. For higher
strength levels alloying elements, e.g.
Al and V have to be added. Ti3Al2,5V has
a tensile strength of minimum 620MPa in
annealed condition and minimum 860 MPa
in the as cold worked and stress relieved
condition. The CP-titanium grades are
nominally all alpha in structure, whereas
many of the titanium alloys have a two
phase alpha + beta structure. There are
also titanium alloys with high alloying
additions having an entire beta phase
structure. While alpha alloys cannot be
heat treated to increase strength, the
addition of 2,5% copper would result in
a material which responds to solution
treatment and ageing in a similar way
to aluminium-copper.